Control of Air Flow as Part of Thermal Insulation Manufacturer s Instructions to Achieve Energy Efficiency of Any Building
Address the role of insulation in a home Today s Presentation Review common types of insulation used in homes Discuss air infiltration and where it typically occurs in a home Summarize recent research conducted by the NAHB Research Center
Insulation is installed first, and foremost, to retard the flow of heat. Insulation: Is a primary contributor to an energy efficient home. Adds to the comfort of a home. Homes are warmer in the winter and cooler in the summer because they are insulated. Provides noise control a benefit that is becoming a highly sought after feature in new homes.
All insulations must be rated by R-value. R-value is the measure of resistance to heat flow. the higher the R-value, the better the insulation material s ability to resist the flow of heat. The FTC requires R-value claims be based on the specific ASTM test methods listed in 16 CFR 460. The FTC recognizes R-value as the single major performance property for consumers to compare insulation products that perform the same function. Any claims that insulation R-value can be discounted or enhanced due to air infiltration capabilities are misleading. R-value and air infiltration are two separate and distinct issues that must be addressed in different steps by the builder.
Common Types of Insulation Used in Today s Homes Insulation Insulation Spray Applied Insulation Insulation
Insulation Does Not Stop Air Infiltration Research consistently demonstrates that insulation alone does not stop air infiltration into the home. Insulation may reduce air movement through the wall cavity, but most air infiltration occurs in other areas. Building scientists recognize that just having an air impermeable insulation does not make a home air tight.
Leaks occur in many places in buildings Most of the air leakage happens around or through penetrations Most air does not pass through insulated wall cavities. Testing has shown that only 14% of the air infiltration in a home occurs through the wall cavity. Air Infiltration Happens! EPA: www.energystar.gov
Air Infiltration of Wood Frame Walls NAHB Research Center May 2009
Air Infiltration of Wood Frame Walls Purpose: To compare the air infiltration through a common stud wall With different types of insulation With and without house wrap And on a stud wall that included a band joist
Air Infiltration of Wood Frame Walls R-13 fiber glass batts R-15 fiber glass blown-in insulation R-13 cellulose - damp spray R-13 spray foam insulation
Air Infiltration of Wood Frame Walls Test Details ASTM E1677-05 Standard Specification for an Air Retarder Material or System for Low- Rise Framed Building Walls 8 x 8 wall 2 x 4 framing 16 o.c. Single bottom plates double top plates Single gang electrical box with wiring holes through studs OSB with 1/8 gap, nailed per IRC Drywall installed on the interior with paper tape and a skim coat of joint compound
Air Infiltration of Wood Frame Walls Additional Wall Test with Band Joist
Insulation Installation Details Control Wall R-value Insulation System Test Details N/A None No house wrap N/A None House wrap-taped
Insulation Wall R-Value Insulation System Test Details R-13 Inset Stapled No house wrap R-13 Inset Stapled House wrap R-13 Inset Stapled House wrap-taped R-13 Face Stapled House wrap-taped R-15 /FG House wrap-taped
Insulation Wall R-value Insulation System Test Details R-13 Damp Spray No house wrap R-13 Damp Spray House wrap R-13 Damp Spray House wrap-taped
Insulation Wall R-value Insulation System Test Details R-13 0.5 pcf spray foam No house wrap R-13 0.5 pcf spray foam House wrap R-13 0.5 pcf spray foam House wrap-taped
Maximum Permissible Air Leakage Rate ASHRAE 90.1 has proposed requirements of 0.04 cubic feet per minute per square foot (cfm/ft 2 ) for an air barrier assembly when tested in accordance with ASTM E 1677 at 75 Pascal (0.3 of water). Assuming an 8 by 8 test sample wall area, the maximum permissible air leakage rate would be 2.52 cubic feet per minute (0.04 cfm/sf x 64 sf). The following slides depicting the NAHB Research Center test results have a dashed line at 2.52 cubic feet per minute mark to show which assemblies would meet this requirement. NOTE The NAHB Research Center report does not state that walls with less than 2.52 cubic feet per minute are considered air tight. This is simply a reference mark showing which assemblies would meet the proposed ASHRAE 90.1 requirements for an air barrier assembly.
Results: Control Wall R-value Insulation Test Details cfm@0.1 cfm@0.3 N/A None No house wrap 6.2 12.3 N/A None House wraptaped 0.26 0.0
Face Stapled Inset Stapled Results: Insulation Wall R-value Insulation Test Details cfm@0.1 cfm@0.3 R-13 Inset Stapled No house wrap 3.6 7.9 R-13 Inset Stapled House wrapno tape 1.1 2.9 R-13 Inset Stapled House wraptaped R-13 Faced Stapled House wraptaped R-15 /FG House wraptaped 0.4 0.4 0.26 0.4 0.04 0.1
Results: Insulation Wall R-value Insulation Test Details cfm@0.1 cfm@0.3 R-13 Damp Spray No house wrap 1.29 2.7 R-13 Damp Spray House wrap 0.41 0.08 R-13 Damp Spray House wrap-taped 0.08 0.0
Results: Wall R-value Insulation Test Details cfm@0.1 cfm@0.3 R-13 0.5 pcf No house wrap 0.0 0.1 R-13 0.5 pcf House wrap 0.0 0.0 R-13 0.5 pcf House wraptaped 0.0 0.0
All Inclusive - Test Wall Results 8x8 Wall With and Without House Wrap
Importance of Sealing All Air Infiltration Paths The air infiltration results in the next slide showing walls insulated with fiber glass and spray foam were done with 2 different wall frame/floor joist assemblies. Therefore it is incorrect to conclude that fiber glass walls with band joists are tighter than foam walls. This only shows that this one fiber glass wall was tighter than the foam wall tested. Because these were 2 different frame assemblies it is likely the untreated joint between the wall frame and the floor sheathing in the foam wall allowed more air infiltration than that in the fiber glass wall. These test results demonstrate the importance of air sealing all air infiltration paths -regardless of the type of insulation used in the wall cavities and band joist assemblies.
Wall 2 Wall 1 Air Infiltration & Insulation R- value Test Wall With Band Joists s & R-13 FG Inset Stapled R-13 FG Inset Stapled R-13 FG Inset Stapled Insulation Test Details cfm@0.1 cfm@0.3 Band joist-no wrap 7.2 14.1 Band joist-house wrap Band joist- wrap + tape 2.06 3.7 1.23 2.1 R-13 Band joist-no wrap 15+ * 15+* R-13 Band joist-house wrap R-13 Band joist- wrap + tape 0.87 1.3 0.56 0.8 Air infiltration rate exceeded the 15 cfm measurement capability of the system Max
Insulation FG Inset FG Inset FG Face Stapled Blown-In FG Does Caulking Make A Difference? 8x8 Wall - With and Without House Wrap - Caulked OSB Test Details No house wrap House wrap taped House wrap -taped House wrap -taped No Caulk cfm@0.1 Low pressure Caulked cfm@0.1 Low pressure No Caulk cfm@0.3 High pressure 3.6 0.83 7.9 1.2 0.40 0.16 0.4* 0.0* 0.26 0.16 0.4 0.1 0.04 0.00 0.1* 0.2* * Data is not consistent due to tolerance of measurement equipment Caulked cfm@0.3 High pressure
Does Caulking Make A Difference? Air Infiltration is significantly reduced simply by caulking and sealing penetrations and construction gaps prior to and during the installation of the insulation package.
Conclusion Air sealing using taped house wrap or caulk effectively reduced air infiltration to near zero for the air permeable insulated wall specimens tested.